I believe that Firefly’s springs are a bit too squat to utilize her maximum length of draw.  That is too say,  the springs would need to be longer to make use of her full 60″ draw capacity.  Her current springs would be pushing draw weights near 7,000 lbs if I were to take the draw to the full sixty inches. These short springs seem ideally suited to shorter draw lengths.

Shorter draw lengths have many possible advantages.  It may be possible to reduce the overall length of the machine by a couple of feet.  The original Orsova machine was unearthed in the remains of a tower.   If standing duty in some kind of cramped guard tower was a major function in their original conception,  these late model, iron framed ballistas may have been quite compact little units.  ……… No worries on Firefly’s long legged stature, though.  She was built for research.  Overcapacity is a plus, at the moment.

If I apply torsion all around by another 7 1/2 degrees, and be careful to adjust the draw length to keep the draw weight around 3700 lbs, this will insure the machine is not overstressed.  No harm, no foul.  At the moment some experiments along this line seem like a no brainer.  The benefits might be exponential.

Modelmaking is revealing when not limited by too much theory.  Observation precedes creation.

One Response to “At last….. a no brainer.”


  1. Captn harpoon says:

    Excerpt from Romanarmytalk, V.G Hart Paper discussion Oct 27,2010 by Warhammer1…

    -“It only serves then to reason, that if the Hatra was first generation (inswinger)with 105 degrees of rotation, and given that movement past 90 takes up string slack and reintroduces it into the release, advancing the entire 105 degrees of rotation another 20 degrees to the outside would totally eliminate this perceived ineffeciency, as well as changing the entire range of arm rotation to amount of string draw. Given that any bundle material however wound has a terminal velocity assigned to it, peformance gains must lie in the design and engineering.

    I will study the paper more, but without someone to argue/discuss/dispute this paper (and my arguments), Im afraid my work and writing are fairly pointless. If Samuli is here, please join in with your thoughts. It is clear to me that the formulas for the outswinger MUST vary to that of the inswinger. The inswinger MUST have a longer spring to take full advantage of the extra rotation available.

    Thus, constructing identical machines with the exception of the direction of pull the arms take, for this test seems flawed somehow, and does not properly address the true advantages of the inswinger dynamics superiority. Inswingers, because of the extreme amount of rotation possible should have a much longer spring. It need not be larger in diameter, but certainly it should be taller, while the arms should decrease in length.

    Without taller springs if both machines were equally pretentioned at rest, the Hatra at 105 degrees would generate a final draw weight expressed as a multiple to that of the Palintone. I doubt if the little machine could withstand the structural load, and would almost certainly result in the “evil huddling” (not to mention stuctural failure) Philon spoke of as the rope gets the snot stretched outta them, and knocks the axis off center.

    The unusually tall spring bundles depicted on Trajans column are not needed for outswingers with their relatively small rotation, and the extra height would detract from performance as more rotation would be required to generate and adequate twisting action. Im also pretty sure some lacked sliders, but instead had a groove for the sliding and winched trigger block. This is a first draft, will edit later if anyone cares as Im sure I made a few mistakes to correct on a later edit.”

Leave a Reply